In the case of increased safety requirements, electronic lock systems are used which operate, for example, by means of electromagnetic waves. In particular in the case of motor vehicles, such lock systems are used as door locking systems for the access authorization and/or as ignition lock systems, steering wheel locks, immobilizers or the like for the driving authorization.
Lock systems of this kind are known from DE 43 40 260 A1. The lock system is composed of a first device which has at least two states and is embodied as a control device for unlocking and/or locking the car doors, the ignition lock or the like, and of an associated second device which is embodied in the manner of an electronic key. The two devices have, for the operation thereof in accordance with the regulations, transmitters and/or receivers for transmitting the electromagnetic signals. During operation according to the regulations, at least one signal can be transmitted as an encoded operating signal between the key and the control device for authenticating the key, with the result that after positive evaluation of the transmitted operating signal and therefore in the case of an authorized key it is possible to bring about a change in the state of the control device.
Such lock systems are also further developed with what are referred to as “Keyless” functionalities. Therefore, in the “KeylessEntry” functionality, there is no longer any need for manual activation of the electronic key by the user. It is sufficient that the user carries the key on his person. The operating signal is then transmitted automatically between the two devices for the access authorization when the user is located in a range of action located in the vicinity of the motor vehicle and activates, for example, the door handle on the car door. Likewise, these lock systems can have a “KeylessGo” functionality, wherein the operating signal for the driving authorization is transmitted automatically between the two devices when the user is located inside the motor vehicle and activates, for example, a start/stop key in the dashboard. In order to transmit the signals, at least one antenna, which can interact with an oscillatory circuit for at least one of the signals, is assigned to the first device.
With these keyless lock systems, it is necessary to take the precaution that in the event of a failure of the keyless functionality, for example, in the case of an empty battery in the electronic key, an emergency operating mode of the motor vehicle is made possible. Therefore, in this case the access to the motor vehicle can be made possible by means of a mechanical emergency key by virtue of the fact that a mechanical door lock is located on a car door. Furthermore, an emergency driving authorization means may be present by virtue of the fact that the electronic key can be plugged into an ignition lock located in the vehicle for the activation thereof. It is also known that in such an emergency the electronic key interacts with an additional transponder reading unit, located in the vehicle, for the driving authorization. However, the provision of such an emergency functionality requires a certain amount of complexity as well as additional costs.